Do you understand snatch blocks...

[p38arover]

...and pulleys.

I do because we studied them in high school in the Applied Maths subject of Mechanics.

Maybe a Smarter Every Day video might help.


https://www.youtube.com/watch?v=M2w3NZzPwOM

[Homestar]

Watched that yesterday, really well explained. 👍

[Blknight.aus]

I'm just going to wait here with the popcorn for the inevitable 2:1 doesnt work, or you cant do that because you reverse the rope....

[austastar]

Hi,

Cheershttps://uploads.tapatalk-cdn.com/20191207/806c32a81b492dafdd11e1e84dca2f13.jpg

[PhilipA]

Sigh!
I remember the last thread on this in when 2007?.

it went on FOR EVAH!

But I guess it will not hurt to edumacate our younger members.
Regards PhilipA

[Blknight.aus]

Sigh!
I remember the last thread on this in when 2007?.

it went on FOR EVAH!

But I guess it will not hurt to edumacate our younger members.
Regards PhilipA

and bridged to other threads


Hand vs electric winch: solo travelling (https://www.aulro.com/afvb/recovery/225807-hand-vs-electric-winch-solo-travelling-3.html)

[roverrescue]

Ahhhhh

An ex-rigger I know of would be so upset at that video

The presenter hooked up a pulley on a tree and the hook back to the winch and then had the audacity to claim Mech.Advantge

But all riggers know that Einstein’s relativity Of motion does not apply to Rigging
And unless the block is in the “moving” component there is no MA


I think that’s the AULRo summary at hand???

S

[Slunnie]

Ahhhhh

An ex-rigger I know of would be so upset at that video

The presenter hooked up a pulley on a tree and the hook back to the winch and then had the audacity to claim Mech.Advantge

But all riggers know that Einstein’s relativity Of motion does not apply to Rigging
And unless the block is in the “moving” component there is no MA


I think that’s the AULRo summary at hand???

S
I think thats incorrect. I had a very quick look at the post and I think pretty much everybody who has winched with a snatch block will agree that you do get a 2:1 MA with the snatch block on a tree. Whether the 4WD moves to the tree or the tree moves to the 4WD, the system doesn't know.
portable electric winches (https://www.aulro.com/afvb/recovery/152013-portable-electric-winches.html)

They are saying the middle picture below produces no MA?

https://www.arrivealive.co.za/images/4x4/24.jpg

This is a more accurate description.



https://www.aulro.com/afvb/images/imported/2012/06/995.jpg

[vnx205]

I think that's incorrect.



I think his summary was tongue in cheek.

I think he was reminding us of the argument we used to see on AULRO.

I think he knows that what you are saying is right.

[roverrescue]

Yeah apologies Simon - very very tongue in cheek

Other than actually winching a metric **** tonne of times I actually did physics at university ;)

I’m not a rigger




Hmmm I wonder though if I’ve got the ball rolling again

S

[Slunnie]

Boom, straignt over my head and totally missed that! Sorry! :Rolling::oops2:

I have to admit, I also pulled out my Uni textbooks thinking I was going to get a metal rewrite and trying to work out WTF this was about because it didn't make sense to anything I learnt or had done either. :blink::lol:

[Slunnie]

Yeah apologies Simon - very very tongue in cheek

Other than actually winching a metric **** tonne of times I actually did physics at university ;)

I’m not a rigger




Hmmm I wonder though if I’ve got the ball rolling again

S

Up an inclined plane due to the earths rotational forces? :lol2: OK, I shudup while I'm behind. :lol2:

[4bee]

His quote, "Any day is a good day when you can use a snatch block"

He really should have added............


"An even better day is when you don't have the need to."[smilebigeye]

[DeanoH]

So if your typical ARB (for example) snatch block is rated at 8000 Kg (17636 lb) and your typical 4WD Supastore winch is rated at 12000 lb (5443 Kg) does this mean that when trying to move the immovable object (bogged to the gills vehicle) that the snatch block can be overloaded with a possible 24000 lb (10886 Kg) pull ?

I've noticed that some American snatch blocks have parallel lines etched into their side plates so that over load deformity around the 'eye' of the snatch block is easily identified.

It's worth noting that a common use of a snatch block is to easily change the direction of pull and that when doing this the 2:1 mechanical advantage ratio does not apply.

Deano :)

[roverrescue]

Snatch Block will have a SWL of 8000kg with a safety factor of 5
So ultimate limit of 40,000kg

Winches are “rated max pull” first layer of the drum.
So a 12,000lb with Dyneema will barely apply 5450kg of pull as dyneema you’ll need at least a few wraps on the drum to grip.

Soooo in short - winch will stall well before any risk to hardware


Snatch block anecdote, when the tojo 200 series first came out
Couple mates and I went chasing Barra in February on private property
To get to the waterhole we had to pass through a tea tree swamp.

130 defender and dual cab hilux both drove through fine
200 following was clearly too heavy for the swamp and went to the gills

Recovery took hours - in the end we had defender and hilux chained to trees at rear
Double line to cruiser and two winches just above stall dragging 200 through the crust.
Ended up cutting down about 20 saplings and built a road to hard ground

We did end up catching good Barra
After that incident I bought another 100m of Dyneema
Can never have enough string or blocks

S

[Blknight.aus]

So if your typical ARB (for example) snatch block is rated at 8000 Kg (17636 lb) and your typical 4WD Supastore winch is rated at 12000 lb (5443 Kg) does this mean that when trying to move the immovable object (bogged to the gills vehicle) that the snatch block can be overloaded with a possible 24000 lb (10886 Kg) pull ?



Correct. (ish)

the snatch block is rated for the max stress it can handle on the eye.
The ropes running to handle no less than half this
The winch (or line if you're doing a sneaky 4:1 by compounding snatchblocks) pulling on the block needs to pull no more than 1/2 the snatch block rated limit (this number goes down if you go past about 15 degrees off parallel)

Be careful with your snatck block SF, ones not rated for lifting will have a SF of 2, rated for lifting 5.

If you've set up the recovery properly ,the second weakest primary element in the whole system should be the winding force of the winch, the weakest element being the resistance of the object you're trying to move (and no I'm not going into compounding and multiple anchor points I'm only talking about a simple single line and double line pull)

[Bigbjorn]

In the Merchant Navy feminine sanitary products were known as snatch blocks.[bigwhistle]

[4bee]

In the Merchant Navy feminine sanitary products were known as snatch blocks.[bigwhistle]


Trust you to bring a bit of class to a thread.[biggrin]

I assume you didn't mean the ones on the Cargo handling gear either.

[Milton477]

In the Merchant Navy feminine sanitary products were known as snatch blocks.[bigwhistle]

We can't unsee that now can we?

[steveG]

<snip>
Recovery took hours - in the end we had defender and hilux chained to trees at rear
Double line to cruiser and two winches just above stall dragging 200 through the crust.
Ended up cutting down about 20 saplings and built a road to hard ground

We did end up catching good Barra
After that incident I bought another 100m of Dyneema
Can never have enough string or blocks

S

So in theory with enough rope and enough blocks you could pull out a Tank?
[tonguewink]

Steve

[roverrescue]

Hehehehe

But only if said tank was recovered in a direct line with the winch
Any off axis pull WOULD result in certain death

S

[gruntfuttock]

I remember talking to an old farmer, he had a big red gum blocking a creek and it was causing damage. Not having anything big enough to pull it out or a saw that would handle it he got out a little 2hp Roseberry hit and miss rigged up pullies and wire rope every where and set it going. It took about 10 days to pull that tree out but it did. Every day he would go down and re rig everything.
Please don’t ask how he had it rigged or how many pullies he had cause I don’t know

[barney]

I was surprised at how many winch-equipped "experts" in the club had no idea about what could be achieved with a snatch block or two, or how to rig anything other than a straight pull.

[fredd63]

In the Merchant Navy feminine sanitary products were known as snatch blocks.[bigwhistle]
In the army, we called them man hole covers

[Blknight.aus]

In the Merchant Navy feminine sanitary products were known as snatch blocks.[bigwhistle]


In the army, we called them man hole covers

And the air force called them flap shrouds

[cripesamighty]

And the air force called them flap shrouds


And who said AULRO wasn't a place of learning...

[4bee]

Ed Zackerly.
You never know when one might be called to appear on Wheel of Fortune, Hard Quiz or even Mastermind & be asked any one of those subjects. Acceptance speech could start by saying "I owe my success to all my friends from AULRO yada yada yada"[biggrin]

[4bee]

I was surprised at how many winch-equipped "experts" in the club had no idea about what could be achieved with a snatch block or two, or how to rig anything other than a straight pull.


They would be the dangerous crowd then? [bigsad]

[ian4002000]

Best book and info i have read on winches and how to use them including side pulls etc is the Four Wheel Drive Handbook by Robert Pepper. It is a great book with heaps of info.
Yes you can easily overload winches and gear using snatch blocks. You also can reduce a lot of the puuling load of stuck vehicles many times by using a shovel and brains .

Ian
Bittern

[4bee]

From what little I've seen of that, brains are not normally in gear at those times when everyone is suddenly an expert & trying to get in on the act to show their mates just how ****ing great they are.[bigsad]

[trout1105]

As in Any other stressfull situation when attempting a recovery the Wisest thing to do is to take a few moments and Really THINK about what you are about to do and then Calmly go about your recovery, a few of the Old Timers that I learnt off would sit down and have a cup of tea before they would affect a repair or recovery.
I wish i had a quid for every time i have seen people running around like headless chooks when they get stuck/bogged doing completely stupid things (sometimes life threatening) without any sort of plan because they haven't sat down and thought about what they are doing because they are in such a tearing hurry.
Then we have the crews that have ALL the flash gear But NFI how to use it correctly and more importantly Safely.
IF you are going to be spending time driving off road or even just driving down the beach then it makes a lot of sense to practice your recovery methods (including the use of snatch blocks) because eventually you WILL get stuck/bogged and that practice WILL make your recovery easier, faster and more importantly Safer.
Snatch blocks are a fantastic bit of kit, Not only do they give you more pulling power they also take a Lot of strain off your winch and the very Last thing you want is a burnt out winch in the middle of a recovery.

[Lionelgee]

Hello All,

My little proving ground - the intermittent creek claimed another victim a couple of days ago. One stock standard Defender 110. The creek used to dry out regularly. However, with my neighbour building two large irrigation dams either side of my property, the creek now regularly carries water. The black peat soil bottom of the creek let me through once. The "that was fun - let's do that again" second run was my undoing. The crust broke, and down went the wheels. Despite the Defender being in four wheel drive, low - there in the creek it stayed. Luckily the engine was out on the high side and stayed nice and dry.

I do not have any winches fitted to a vehicle. So I decided it was time to buy a Tirfor style hand winch and three snatch blocks. Luckily there was a very handy gum tree close by. It makes for a damn good anchor point! Fortuitously, it was one of the trees we planted just after we bought the place!

The bogging occurred just on dusk - so that night I watched some YouTube clips. The very first video I watched; unbeknown to me at the time, was the very same clip that Ron posted at the start of this thread! I also watched a clip about using Tirfor style hand winches. It has been decades since I used a proper brand name "Tirfor" winch while working in Arboriculture = tree surgery. Where I used ropes and winches regularly as part of my former trade.

Everything was hooked up and I had a workout on the winch handle. Slowly and steadily with some gurgling from the creek - out rolled the Defender.

With the presence of water in the creek becoming more frequent it looks like I have to install a culvert or a couple truck loads of rocks to make a causeway. The creek separates two sides of my block and the other side is where the soil stockpiles are. I would prefer not to have to winch out the Defender again!

Kind regards
Lionel

[4bee]

I fell out with my French neighbour over this sort of thing. He seems to do what he likes with stones etc in the watercourse but does not give a flying **** about anyone downstream. It always has consequences.

The fact that it has been pointed out to him he needs Approvals etc from the relevant body before he can bugger.
ise about with the watercourse seems to escape him.


Silt buildup in the Dam leads to ("What silt?") The dam will always be below his vineyard & he is still developing this.

Stupid him places restrictions in the water course, oblivious to the fact that soil will always build up above it so a further problem later on, so in will come the excavators to clear that but no way can they clear the dam of the silt & they will make even more.

[Lionelgee]

I fell out with my French neighbour over this sort of thing. He seems to do what he likes with stones etc in the watercourse but does not give a flying **** about anyone downstream. It always has consequences.

The fact that it has been pointed out to him he needs Approvals etc from the relevant body before he can bugger.
ise about with the watercourse seems to escape him.


Silt buildup in the Dam leads to ("What silt?") The dam will always be below his vineyard & he is still developing this.

Stupid him places restrictions in the water course, oblivious to the fact that soil will always build up above it so a further problem later on, so in will come the excavators to clear that but no way can they clear the dam of the silt & they will make even more.

Hello 4bee,

Yes neighbours - said party decided that the down stream side of creek/watercourse/drain was not deep enough. So excavators appeared right on the boundary and dug the profile down deeper. No attempt was made in building a retaining wall. Since then each time it rains - or water is released from the top dam - I have lost about the size of my Commodore wagon worth of soil as my land erodes away.

Kind regards
Lionel

[4bee]

HELL!

I thought I had got through to Napoleon during our last little blue (aka Battle of Waterloo) when he finally laid some straw bales down stream due to my insistence which caught a lot of crap, so in my innocence I thought he would do likewise this time. Oooohhh noooooo, not him & I was a bit tardy about recce-ing the site & then it was too late & if he did think about it he'd be looking at cost.


I should have realised he was up to no good the way he fell over us when we were Social Distancing recently. He actually called into shops for us.

Time like this one needs the likes of the Duke of Wellington & 40,000 troops to knock on his Port. [bigrolf]

The irony of this is that he wanted to buy our dam when he bought the attached paddock for vines. & people who know about these things advised us not to sell due to possible demarcation & maintenance disputes in the future.

Ce'st la vie